The present invention relates generally to the field of steam ovens for steam-cooking foods, and more particularly to improvements for steam ovens.
Commercial and household steam ovens have been used for years to steam-cook foods, including rice, poultry and vegetables. While the size and shape of known steam ovens may vary depending on their particular use (e.g., restaurant versus home), steam ovens generally include a boiling reservoir in which water is converted into steam and a food-steaming compartment.
In one type of conventional steam oven, a user pours water directly into the boiling reservoir when food steaming is desired. Typically, the boiling reservoir is located inside the steam oven, and a door, panel or similar structure must be opened or removed to gain access to the boiling reservoir. Generally, the water is boiled in the boiling reservoir by means of a heating element positioned in the boiling reservoir.
A second type of conventional steam oven includes a separate water tank that communicates with the reservoir. In many designs, the water tank is accessible from the exterior of the steam oven to permit ready filling of the water tank by the user. Typically, the water tank includes some sort of discharge valve to regulate the flow of water into the reservoir. Otherwise, water could overflow the boiling reservoir and create a safety hazard.
One type of conventional water tank is designed to hold water therein by means of a vacuum formed in the top of the water tank and a water discharge valve that is responsive to water level changes in the given appliance. When the water tank is filled and the water discharge valve is opened, the open water discharge valve allows air to flow into the water tank (i.e., from an area of atmospheric pressure to an area of zero or near-zero pressure). Consequently, in a steam oven, water is forced to flow from the water tank into the boiling reservoir. The water flow into the boiling reservoir continues until the water level in the boiling reservoir covers the opening of the water discharge valve. At this point, the air flow through the water discharge valve into the water tank is stopped, and the water flow from the water tank into the boiling reservoir is terminated. After sufficient water is converted into steam by the heating element to uncover the opening of the discharge valve, air is once again able to flow into the water tank to cause water to be discharged therefrom into the boiling reservoir. This process continues until all of the water is drained from the water tank or the steam oven is deactivated.
In steam ovens having separate water tanks and boiling reservoirs, untimely and unregulated water flow from the water tanks can occur. Specifically, as the heating element heats and eventually boils the water in the water reservoir, the water becomes increasingly agitated. As the agitation increases to a maximum (i.e., where the water is at a complete boil), the water adjacent to the water discharge valve contorts and uncovers, with steadily increasing frequency, the opening of the water discharge valve, even though the water level, in a normal (i.e., unagitated) state, is such that the valve opening would normally be covered. As a result, water is discharged from the water tank into a boiling reservoir that already contains its operating complement of water. Consequently, an overflow of water from the boiling reservoir may occur, which can cause a safety hazard for users of the steam oven.